Investigators claim information ‘could only be supplied by the police or the security services’

Investigators into the systematic blacklisting of construction workers have claimed information held on workers “could only be supplied by the police or the security services”.

The Information Commissioner’s Office, which is investigating a database of files on 3,200 blacklisted workers that was unearthed in 2009, told the Observer the level of detail uncovered on some workers “wouldn’t have formed anything other than a police record”.

The claim is likely to intensify scrutiny of the police, which has come under fire in recent weeks for its close relationship with private corporations, particularly News International.

Over 100 workers are currently preparing a High Court class action against some of the construction firms implicated in the blacklisting scandal.

Major firms including Balfour Beatty, Sir Robert McAlpine and Laing O’Rourke were found to have paid for access to blacklists three years ago. However, Building does not have any evidence that these firms will be targeted by the writ.

A raid on the offices of a firm known as the Consulting Association in Droitwich in 2009 revealed more than 40 firms were paying an annual fee to access information on 3,213 workers’ union history, personal relationships and employment history.